JPH0727590B2 - Real-time adaptive bullet identification fire sensor - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates generally to fire or explosion detection and fire suppression systems, and more particularly to real-time systems with appropriate identification for high energy anti-tank missiles.

BACKGROUND OF THE INVENTION Fire detection and extinguishing systems are generally well known which are capable of responding to the occurrence of a fire or explosion and producing output control signals for operating a fire extinguishing device. In military applications, for example, vehicles such as armored vehicles and tanks (vehicl
e) It is desirable to distinguish between the thermal energy generated by a hydrocarbon fire caused by the explosion of an internal fuel tank and the thermal energy generated by a “high energy anti-tank” (heat generating) bullet. Exothermic bullets induce transient high-energy radiation levels and high temperatures in excess of 5000 °. Such high energy output is generated not only by the bullet itself, but also by a secondary reaction between the bullet and the armor.
This secondary reaction is theorized as a self-sustaining reaction. If the bullet penetrates the fuel container and ignites the fuel inside, the heating bullet is highly likely to cause a hydrocarbon fire. Therefore, it is desirable to prohibit operation of the fire suppression system if the heating bullet penetrates the armor plate of the vehicle but does not explode the fuel tank and thus does not induce a secondary hydrocarbon fire.

US Patent, Patent No. 3,825,754 (July 23, 1974)
The inventor: Cinzori) disclosed a detection system, in particular for detecting heat-generating bullets and having a sensing means which responds to such bullet detection by inhibiting the operation of the hydrocarbon fire detection means for a certain period of time. Suitable for many applications, it requires external coding for various armor types. This system also requires first and second preset threshold levels and does not take into account the thickness of the armor equipped on the vehicle containing the system. Also, the size and energy of the projecting bullet is narrow and the dynamic range of the bullet detector is generally not sufficient to measure high intensity peaks for certain heat bullets. Thus, this detection circuit is unable to measure certain high intensity peaks and is saturated by the high energy associated with the bullet. Therefore, it is desirable that the fire sensor system is prohibited from operating for a certain period of time before the occurrence of the secondary fire can be detected.

U.S. application number 4,101,767 (July 18, 1978, inventor: Lennington) describes a fire identification sensor with detection means for identifying hydrocarbon fires and the high energy of exploding bullets that do not cause hydrocarbon fires. Explained. There are some drawbacks inherent in this system. For example,
Immediate identification of low energy bullets below 2500 ° K at color temperature is not possible. Also, this system cannot immediately identify whether a bullet has penetrated the thick armor that keeps the color temperature of the bullet below 2400 ° K.
Also, the dynamic range of this bullet detector is not sufficient because the circuit saturates in high intensity measurements for many bullets. Therefore, this sensor system must be disabled for a few milliseconds before it can detect a secondary fire.

SUMMARY OF THE INVENTION In order to overcome the above drawbacks, an adaptive bullet identification fire sensor system according to the present invention is a fire occurrence detecting means 28 for generating an output signal for operating a fire extinguishing system 29 when a fire occurs, The output signal is connected and disconnected from the fire suppression system 29 by switch means 24; thermal energy for detecting the thermal energy output of the fire product and generating an output signal indicative of the magnitude of the thermal energy of the fire product. Control means 20 connected to the output of the detection means 12 and the thermal energy detection means 12 to determine the magnitude of the thermal energy of the fire product, and further connected to the switch means 24 to control the operation of the switch means 24. The control means 20 controls the fire suppression system when the rate of change of the thermal energy exceeds a predetermined threshold value.
The output signal for operating 29 is decoupled from the fire suppression system 29, such that after a predetermined time after the rate of change of thermal energy exceeds a predetermined threshold value, the value of the thermal energy reaches during a predetermined time interval. Against the maximum value
Means 20 for controlling the switch means so that the fire extinguishing operation signal is reconnected to the fire extinguishing system 29 when reduced to a value less than or equal to a predetermined percentage.

The fire detection system according to the apparatus and method of the present invention distinguishes between a heating bullet that does not induce a secondary fire and a heating bullet that induces a secondary fire, which overcomes the problems of the prior art described above, and Benefits arise. The system according to the present invention measures the peak intensity of the penetrating heating bullets to determine the second threshold level, which is subsequently used in detecting the resulting hydrocarbon fire. The system also performs a statistical analysis of the characteristic slope of the thermal signature of the bullet to determine if a secondary fire will occur.

The system according to the invention distinguishes between heating bullets that cause a fuel fire and heating bullets that do not cause such a fire, regardless of the type of bullet and the type of armor used in the vehicle. That is, the system does not require calculations or adjustments regarding the type or thickness of armor plate used in the vehicle. Also, the system of the present invention is
Effectively determine in real time the second threshold level used in determining whether a bullet will cause a secondary fire. Thus, the present invention can be used to effectively distinguish between different sizes and energy levels of heating bullets. The present invention employs a wide dynamic range, logarithmic, non-saturating detection circuit, eliminating any requirement to inhibit the output of a fire sensor for a predetermined amount of time. Thus, the problems of conventional systems that require the fire sensor output to be disabled for a few milliseconds after the bullet detection circuit is saturated are overcome.

The fire detection system according to the present invention can be effectively used for various thicknesses and any type of armor plate, regardless of the size or energy level of the heating bullet. This feature allows one system to be used for all types of vehicles without any external adjustment to match the particular armor plate type employed in the vehicle.

In the preferred embodiment of the present invention, a bullet discriminating fire sensor system has a logarithmic detection circuit coupled to an analog to digital converter to convert the detector output voltage signal to digital form. The digital output signal is processed by a microprocessor which has an output for controlling a switch means located between the fire sensor and the fire suppression system operated by the fire sensor.
Various software routines are executed by the microprocessor to monitor the detector output and control the switching means. Based on the detector output signal exceeding a predetermined first threshold value, the microprocessor can operate a timer. Subsequently, the dV / dT of the bullet signal is calculated and dV / dT is compared with a predetermined maximum value. If dV / dT exceeds this maximum, the microprocessor will disable the fire sensor output. The threshold is generally exceeded if the heating bullet enters the vehicle without penetrating the fuel container. If the heating bullet penetrates the fuel container, the dV / dT rise time of the bullet signal will generally not exceed this first threshold value and the output of the fire sensor is not prohibited.

In the present invention, the microprocessor is capable of sampling the bullet signal at certain time intervals and performing a statistical analysis of the signal by calculating the average of this signal and the average residual of the previous 16 bullet signals. The average residual of the signal is used to determine the tilt and tilt polarity of the bullet signal to allow detection of secondary fires.

BRIEF DESCRIPTION OF THE DRAWINGS These and other valuable features of the present invention will become apparent in the following description of a preferred embodiment, taken in conjunction with the accompanying drawings.

1 is a block diagram of a compatible bullet identification fire sensor system according to the present invention: FIGS. 2a and 2b are flow charts showing one software routine executed by the data processing means of the present invention: 3, 4, Figures 5, 6, 7 and 8 are graphs of bullet detector output (volts) versus time for various types of situations caused by the entry of a heating bullet into the armored vehicle.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a block diagram illustrating an adaptive bullet identification fire sensor system 10 which is a preferred embodiment of the present invention. The system 10 comprises means for detecting the radiant output of fire products. Such means are associated with radiation detection means such as photodiodes, which have a typical spectral response between 0.7 and 1.0 microns, and have a dynamic range of 100 dB.
The logarithmic form of the detection circuit 12 may be exceeded. The detector 12 has an analog voltage output 14, which is connected to the input of an analog-to-digital converter 16. As is well known, the analog-to-digital converter 16 converts the voltage output 14 of the detector 12 into a digital signal representing the magnitude of the signal voltage. This digital signal is represented as the number of discrete bits transmitted by the data bus 18 and is transmitted to the input of a control means for processing data, such as a microprocessor 20. Of course any suitable data processing means,
Digital signal processor or analog processing circuits, for example, can also be used. The microprocessor 20 has a inhibit output 22 connected to a switch means 24. The switch means 24 is further connected to the output 26 of the fire sensor 28. Accordingly, the microprocessor 20 can open and close the switch means 24 to connect or disconnect the output 26 of the fire sensor 28. The switch means 24 is a semiconductor switch, an electromagnetic relay,
Alternatively, any suitable high speed switch that can be controlled by the microprocessor 20 can be used.
The output 26 of the fire sensor 28 is the armored vehicle (vehicl
e) Appropriate fire extinguishing measures to suppress or extinguish a fire such as a hydrocarbon fire caused by the explosion of the fuel tank inside
Can be connected to 29. For example, fire extinguishing means 29
May be a CO ₂ or Freon cylinder storage device connected to a fast acting active mechanism. Fire sensor 28 is responsive to a particular one or more of the spectral lines for the combustion byproducts of a hydrocarbon fire. In the present invention, it is desirable to prohibit the output of the fire sensor 28 for a certain period of time, such as immediately after receiving a heating bullet in the armored vehicle. Such a prohibition means prevents the fire sensor 28 from activating the fire suppression device 29 when the fire sensor detects the thermal radiation generated by the heating bullet, if the hydrocarbon fire does not occur due to the entry of the heating bullet. Ban.

Microprocessor 20 may execute a number of software routines to perform this useful function of selectively inhibiting the output of fire sensor 28 after the entry of a heating bullet. Microprocessor 20 is provided with memory devices to perform this function, and these memory devices are provided by an address and data bus (not shown) using methods well known to those skilled in the art. Can be accessed.

2a and 2b, some soft routines executed by the microprocessor 20 using the method according to the invention are shown in flowchart form.

After the initial power up of the system, shown in block 30, the microprocessor 20 constantly monitors the output of the detector 12, as shown in block 32. The output value of the detector 12 is
When it is determined that it is above a certain threshold value, such as 0.5 volts, the microprocessor 20 initializes an internal timer to 0 (block 34). After this, the value of the timer is increased by a clock input signal having a constant frequency, for example. Therefore, the value of the timer at a predetermined time point after initialization corresponds to the time from when heat generation is detected.

After a predetermined time (typically 300 microseconds), the heating signal dV /
dT is calculated at block 36. The calculated value of dV / dT is then compared to see if it is equal to or greater than a certain threshold value, such as 2000 volts / second. When it is determined that dV / dT exceeds this value, the microprocessor 20 inhibits the output of the fire sensor 28 (block 40). Existence of dV / dT, which shows this rapid increase rate, is confirmed only when the exothermic circle enters the vehicle without penetrating the fuel container. If the heating rod penetrates the fuel tank, the rate of increase in dV / dT will be much smaller due to the cooling of the bullet due to immersion in the fuel or frame. Therefore, for a rate of rise of 2000 volts / second or less, a secondary fire can occur that does not inhibit the output of the fire sensor and causes the microprocessor 20 to execute a software routine that resets the clock (block 3
8) Then, returning to block 32, the output signal of the detector 12 is continuously monitored.

FIG. 3 shows the temperature characteristic shape, that is, the characteristic, of the exothermic cylinder which did not penetrate the fuel tank when the vehicle entered the vehicle. As you can see, the first threshold level is exceeded in the time of 100 microseconds or less.
For 00 microseconds, dV / dT is well over 2000 volts / second. Due to the bullet traces shown in FIG. 3, the output signal of the sensor is inhibited as in block 40 of FIG.

FIG. 4 shows the thermal characteristics of the exothermic cylinder that penetrates the fuel tank when entering the vehicle. In this case, the output of the detection circuit does not reach the first threshold until about 4.5 milliseconds after the bullet penetrates. This time is sufficient for the fire sensor to respond, but even after the bullet signal exceeds the first threshold level, the slow rise of the dV / dT signal does not inhibit the output of the fire sensor.

By referring again to block 40 of FIG. 2, it can be seen that microprocessor 20 continues to monitor bullet traces and records the highest level reached, after the sensor is inhibited. About 1.after the timer in block 34 starts counting.
After 75 ms, the value of the analog-to-digital converter 16 is then compared with the previous maximum value. If it is determined that the value at this time is less than a predetermined threshold value, eg, 40% of the recorded maximum value, the fire sensor output is enabled (block 44). This enables the sensor output for bullets that plunge into the vehicle and, without penetrating the fuel container, strike the flammable metal inside the fuel container or vehicle. This phenomenon is shown in FIG. During this time (approximately 1.75 ms), if the bullet hits the vehicle and then hits the fuel or combustible metal, the bullet will not reach 40% or less of the maximum energy level reached due to immersion in the fuel or flame. Will be cooled.
Therefore, the sensor is in the secondary fire detectable state.

If, at block 42, the microprocessor 20 determines that the bullet detector signal level is equal to or greater than 40% of the highest recorded level, program flow proceeds to block 48. At block 48, the microprocessor 20 monitors the bullet detector output signal for an additional 3.25 milliseconds and records the peak value and the time of peak occurrence. After this time has elapsed, the microprocessor 20 performs a statistical analysis of the bullet signal. To do this analysis,
The microprocessor 20 samples the bullet signal at intervals of about 100 microseconds and calculates the average value of the signal.

Furthermore, the average residual of the immediately preceding 16 signals is calculated.

About 6.6 ms after the bullet entered, the bullet detector output signal would decrease if no secondary fire had occurred. Therefore, the subsequent bullet signal tilt is used to detect the occurrence of a secondary fire. The average residual polarity of the signal is used to determine the value of the slope.

After collecting 16 samples for 1.6 ms, the fire sensor is ready to output if the average residual of the signal is determined to be positive. In the present invention, the use of the average residue of the signal allows detection of rapid changes in polarity at or near the peak energy level received by the detector. At this time, one or more peak energy levels occur that indicate the maximum potential for a secondary fire. The system therefore automatically and continuously adjusts the sensitivity in relation to the energy and tilt of the bullet signal. This allows the circuit to respond quickly to rapidly rising signals that indicate the onset of an explosion, but the system allows a small increase in signal for a short period of time, such as the bullet detector being exposed to sunlight when the hatch is opened. It does not respond to exposures or to melted armor in the detection area of the detector.

Figure 6 shows the bullet trace characteristics of the secondary fire.
The figure shows the detection signal indicating a small secondary positive tilt caused by a large number of dead bullet traces. Therefore, by using the average residual, the sensor can immediately output in the case of FIG. 6 and keeps the sensor output inhibited for the bullet traces shown in FIG.

Also, in connection with the slope detection of the trace characteristic, the magnitude of the received bullet trace signal must exceed the first threshold to enable sensor output.

In block 52 of Figure 2, the current value of the timer is compared to the value at which the peak value was recorded. Four milliseconds after the peak in intensity, the bullet signal is compared to a second threshold value (block 54). This second threshold value is not a fixed value, but is a peak value +
4 ms x peak value / time function, or Where S _ET is the second energy threshold, τ is the time of the bullet's peak energy, V _PEAK is the bullet's peak amplification (V), and T is the elapsed time for the bullet's plunge.

This second level has an initial value equal to the peak intensity value and then decreases as a function of time until the first threshold value is reached. If it is determined that this signal is equal to or greater than the second threshold of block 54, as indicated by block 56, then this signal is compared to the first threshold value. If this signal is also determined to be greater than the first threshold, then the fire sensor is ready to output (block 44). Therefore, the sensor can be output in the event of a secondary fire, but the bullet will be cooled by being immersed in the frame. This reduction is shown in FIG. If the value of the signal is determined to be less than the first or second threshold values (blocks 54 and 56, respectively), the fire sensor is unable to output. The microprocessor 20 then continues to compare the signal to the second and first levels, setting the polarity of the ramp to 50.
Inspect for 0 milliseconds (block 50), at which time the sensor is ready to output again (block 58).

Based on the above, the apparatus and method of the present invention can solve the above-mentioned problems of the prior art. For example, the present invention eliminates the need to disable the fire sensor due to bullet detector saturation resulting from excessive thermal energy output in the heating bullet. The advantage of using the present invention is that the second threshold value is not a fixed value but is determined by a dynamic method based in part on the elapsed time from the entry of the heating bullet and the peak intensity of the entry bullet. . Furthermore, the present invention does not require special coding or calibration for the type and / or thickness of the armor steel plate. Thus, the system constructed according to the apparatus and method of the present invention can be effectively used with a wide variety of vehicles and does not require any special additions to that particular vehicle.

The above specific time and threshold values are for explanation only, and the practice of the present invention is not limited to these specific time and threshold values. Obviously, numerous modifications to the described embodiments of the invention may be made by those skilled in the art based on the foregoing. Therefore, the present invention is not limited by the embodiments disclosed herein, but only by the appended claims.

Claims (10)

[Claims] 1. A fire occurrence detecting means for generating an output signal for operating a fire extinguishing system when a fire occurs, wherein the output signal is connected to and disconnected from the fire extinguishing system by a switch means; Thermal energy detecting means for detecting a thermal energy output of the fire product and generating an output signal indicating a magnitude of thermal energy of the fire generating material; and thermal energy of the fire product connected to an output of the thermal energy detecting means. Of the fire energy when the rate of change of the thermal energy exceeds a predetermined threshold value, the control means being connected to the switch means and controlling the operation of the switch means. The output signal for operating the fire suppression system is decoupled from the fire suppression system so that the rate of change of thermal energy is at a given threshold. A predetermined time after exceeding the Yorudo value, when the value of the thermal energy which the relative maximum value reached during the predetermined time, decreases to a value below a predetermined percentage,
An adaptive bullet identification fire sensor system comprising: means for controlling the switch means to reconnect the fire suppression operation signal to the fire suppression system. 2. The thermal energy detection means comprises radiation detection means and a logarithmic type detector connected to the radiation detection means, the radiation detection means having a spectral response between 0.7 and 1.0 microns. The system of claim 1 wherein the logarithmic detector circuit has a dynamic range of 100 dB or greater and is capable of representing the radiation intensity received by the radiation detection means. 3. The system according to claim 2, wherein said control means is a data processing means capable of judging the radiation intensity received by said radiation detecting means from the magnitude of the voltage output of said radiation detecting means. . 4. An analog / digital conversion means for converting the voltage output of the radiation detection means into digital data composed of a plurality of digital bits and supplying the digital data to the input of the data processing means. The system according to claim 3, characterized in that 5. A method for selectively inhibiting the operation of the fire suppression system after a high energy bullet rushes into an enclosure equipped with the fire suppression system, the output of a bullet detector being monitored, Determining the time when the output of the bullet detector exceeds a predetermined first threshold value corresponding to the energy indicating the bullet plunge; and measuring the value of the timing means for measuring the elapsed time from the bullet plunge. Initializing ;; monitoring the energy of the bullet for a predetermined first time interval; calculating an increase rate of energy emission for the bullet after the predetermined first time interval; Determining whether the rate of increase is greater than or equal to a predetermined first value; and, if the calculated rate of increase is greater than or equal to the predetermined first value, the fire. Inhibiting the operation of the fire system; monitoring the energy of the bullet for a predetermined second time interval after inhibiting the operation of the system; Recording the maximum energy value reached by energy; comparing the bullet energy at the end of the predetermined second time interval with the maximum energy value recorded in the recording step; Determining whether the energy of the bullet at the end of the second time interval is less than a predetermined percentage of the recorded maximum energy value; and the energy of the bullet is the predetermined energy value of the maximum energy value. Enabling the operation of the fire suppression system if less than a percentage of How. 6. A predetermined third time interval, if the energy of the bullet at the end of the predetermined second time interval is determined to be greater than or equal to the predetermined percentage of the recorded maximum energy value. Monitoring the output of the bullet detector; recording the value of the maximum energy reached by the bullet energy and the time at which the bullet energy reached the maximum energy during the predetermined third time interval. And; to obtain a predetermined number of samples of the bullet detector output,
Sampling the bullet detector output at a predetermined sampling period; calculating an average value of the bullet detector output and an average residual for the predetermined number of samples; detecting the bullet from the polarity of the average residual Determining the polarity of the inclination of the bullet output; determining whether the magnitude of the bullet detector output is greater than or equal to the first threshold value; and, if the inclination of the bullet detector output is determined to be positive And, if the magnitude of the output is greater than or equal to the first threshold value, enabling the fire suppression system. 7. The present time point indicated by the timing means when the inclination of the bullet detector output is determined to be negative or when the magnitude of the output is determined to be smaller than the first threshold value. Comparing with the time when the arrival of the maximum energy is recorded, the current time is calculated as “the time when the arrival of the maximum energy is recorded + the predetermined fourth
A step of determining whether it is equal to or more than "a time interval"; when it is determined that a current time point indicated by the timing means is "a time when the arrival of the maximum energy is recorded + the predetermined fourth time interval" or more, Calculating a second energy threshold level, comparing the value of the bullet detector output with the second energy threshold level, and determining whether the bullet detector output value is greater than or equal to the calculated second energy threshold level. The current value of the bullet detector output is the calculated second value.
When it is determined that the current value of the bullet detector output is higher than the first threshold level when it is determined that the energy is higher than the energy threshold level, the fire suppression system is operable when the current value of the bullet detector output is higher than the first threshold level. 7. The method according to claim 6, further comprising: 8. The second energy threshold level is expressed by the following equation: Where S _ET is the second energy threshold level, τ is the time when the bullet reaches its peak energy, V _PEAK is the peak amplitude of the bullet (volts), and T is the elapsed time from when the bullet rushed. The method of claim 7, wherein the method is: 9. A method for detecting the occurrence of a secondary fire caused by the entry of a high energy anti-tank (heat-generating) bullet into an armored vehicle having an operable fire sensor, the method having a predetermined first threshold value. A step of determining the time of entry of the heat-generating bullet by detecting the increase in heat energy; a step of measuring the increase rate of heat energy of the heat-generating bullet; If exceeded, inhibiting the operation of the fire sensor means; iteratively calculating a second thermal energy threshold value that decreases in value as a function of time, while the current value of the thermal energy of the bullet and the calculated value By comparing each threshold value, the fire sensor means does not detect the thermal energy of the bullet, rather than accidentally. A step of determining when a secondary fire can be detected. 10. The fire detecting means may be able to detect the occurrence of a secondary fire from the step of calculating the average value of the thermal energy of the bullet and the average residual for a predetermined time and the polarity of the slope of the average residual calculated. 10. The method of claim 9 including the step of determining if.